Na(+), K(+)-ATPase content in skeletal muscle of dogs with pituitary-dependent hyperadrenocorticism.

Several hormones regulate Na(+), K(+)-ATPase content in the muscle cell membrane, which is essential for maintaining muscle cell excitability. Chronic glucocorticoid excess is associated with muscle weakness and reduced endurance. We hypothesized that chronic glucocorticoid excess affects Na(+), K(+)-ATPase content in canine skeletal muscle, and contributes to reduced endurance and muscle weakness associated with pituitary-dependent hyperadrenocorticism (PDH) in dogs. Therefore, Na(+), K(+)-ATPase content in skeletal muscle was evaluated before and after hypophysectomy and hormone replacement (cortisone and l-thyroxin) in dogs with PDH (n=13), and in healthy controls (n=6). In addition, baseline and exercise-induced changes in plasma electrolyte concentrations and acid-base balance were evaluated before and after hypophysectomy in dogs with PDH. Na(+), K(+)-ATPase content of gluteal muscle in dogs with PDH was significantly lower than in control dogs (201+/-13pmol/g versus 260+/-8pmol/g wet weight; P<0.01). Similar differences were found in palatine muscle. After hypophysectomy and on hormone replacement, Na(+), K(+)-ATPase was increased (234+/-7pmol/g wet weight). Both plasma pH and base excess in dogs with PDH (7.44+/-0.01; 1.7+/-0.6mmol/l, respectively) were significantly higher (P<0.05) than after hypophysectomy and hormone replacement (7.41+/-0.01; -0.2+/-0.4mmol/l, respectively). Exercise induced respiratory alkalosis, but did not result in hyperkalemia in dogs with PDH. In conclusion, chronic glucocorticoid excess in dogs with PDH is associated with decreased Na(+), K(+)-ATPase content in skeletal muscle. This may contribute to reduce endurance in canine PDH, although dogs with PDH did not exhibit exercise-induced hyperkalemia. Na(+), K(+)-ATPase content normalized to values statistically not different from healthy controls after hypophysectomy and hormone replacement.

Inhibition of inducible nitric oxide synthase improves graft function and reduces tubulointerstitial injury in renal allograft rejection.

Increased levels of nitric oxide (NO) are found in rejecting renal allografts. Inducible NO synthase (iNOS) in infiltrating monocytes/macrophages could lead to NO bursts. NO may modulate the inflammatory response of early rejection due to its high reactivity with superoxide to yield peroxynitrite. To define the role of iNOS in acute renal allograft, rejection effects of the specific iNOS blockers iminoethyl-lysine and 7-butylhexahydro-1H-azepin-2-imine, monohydrochloride on renal function and morphology were investigated in renal allografts. Lewis rats received Brown Norway grafts with one kidney left in situ. All recipients were treated with low dose cyclosporine-A (2.5 mg/kg BW/day s.c.) to allow moderate rejection. In addition, one group received iminoethyl-lysine (10 mg/kg BW/day gavage) and one group received butylhexahydro-azepin-imine (3.4 mg/kg BW/day i.p.). Sham operated Brown Norway donor rats served as baseline controls. Compared to controls, low dose cyclosporine-A decreased glomerular filtration rate (P<0.05) and numerically increased renal vascular resistance. Adding iminoethyl-lysine to cyclosporine-A improved renal hemodynamics. Adding butylhexahydro-azepin-imine to cyclosporine-A practically restored glomerular filtration rate and renal vascular resistance (P<0.05) to control levels. Grafts treated with cyclosporine-A alone showed vascular, glomerular and tubulointerstitial lesions. Adding iminoethyl-lysine or butylhexahydro-azepin-imine to cyclosporine-A did not significantly reduce vascular and glomerular injury, but diminished tubulointerstitial injury as well as nitrotyrosine staining in tubular epithelium (P<0.05). Thus, adding the iNOS blockers iminoethyl-lysine or butylhexahydro-azepin-imine to cyclosporine-A improved graft function and reduced tubulointerstitial lesions.

Endothelial injury: cause and effect of alloimmune inflammation.

This review discusses the concept that endothelial cells may facilitate inflammation, but are also targets of the inflammatory response. Endothelial cells express several molecules that promote leukocyte recruitment, and other molecules, such as MHC class I that enable endothelial injury. Circulating alloantibodies produced following transplantation may also target the endothelium for injury. It has been shown that the expression of select protective genes within endothelial cells, including anti-apoptotic genes, may provide resistance to immune-mediated injury. Thus, an understanding of the mechanisms by which endothelial cells are injured and by which endothelial cells are protected is important for our understanding of allograft rejection.

NFkappaB decoy oligodeoxynucleotides reduce monocyte infiltration in renal allografts.

Monocyte influx secondary to ischemia-reperfusion conditions the renal allograft to rejection by presentation of antigens and production of cytokines. Monocyte influx depends on NFkappaB-dependent transcription of genes encoding adhesion molecules and chemokines. Here we demonstrate that cationic liposomes containing phosphorothioated oligodeoxynucleotides (ODN) with the kappaB binding site serving as competitive binding decoy, can prevent TNF-alpha-induced NFkappaB activity in endothelial cells in vitro. In an allogenic rat kidney transplantation model (BN to LEW), we show that perfusing the renal allograft with this decoy prior to transplantation abolishes nuclear NFkappaB activity in vivo and inhibits VCAM-1 expression in the donor endothelium (P<0.05). At 24 h postreperfusion, periarterial infiltration of monocytes/macrophages was significantly reduced in decoy ODN-treated allografts compared to control allografts (3.7+/-0.7 vs. 9.2+/-1.2 macrophages/vessel; P<0.01). At 72 h, there was a reduction of tubulointerstitial macrophage infiltration in decoy ODN-treated kidneys compared to controls (75.6+/-13.9 vs. 120.0+/-11.2 macrophages/tubulointerstitial area; P<0.05). In conclusion, perfusion of the renal allograft with NFkappaB decoy ODN prior to transplantation decreases the initial inflammatory response in a stringent, nonimmunosuppressed allogenic transplantation model. Therefore, the NFkappaB decoy approach may be useful to explore the role of endothelium and macrophages in graft rejection and may be developed into a graft-specific immunosuppressive strategy allowing reduction of systemic immunosuppression on organ transplantation.